Safety-valve



G. H. CLARK.

SAFETY VALVE.

APPLICATION FILED 00123, 1919.

1,356, 54. Patented Oct. 26,1920.

i \x w U f I i V Y am? 0316 lation lift, and if a large accumulation lift:

UNITED STATES PATENT QOFFI'CE.

eEoEeE HALL CLARK, or CAMBRIDGE, MASSACHUSETTS, AssIsNoE To-enosnr- STEAM GAGE & VALVE COMPANY, OF BOSTON, MASSACHUSETTS, A OORPORA- ,TION' OF MASSACHUSETTS.

To all whom it may concern." 7

Be it known that I, GEORGE HALL CL RK, a citizen of the United States of America, and resident of Cambridge, in the county of Middlesex and State of Massachusetts, have invented new and useful Improvements in Safety-Valves, of which the following is a specification.

My invention relates to safetyvalves forsteam boilers, and has for its objects to provide av valve which will sustain practibe provided for by the valve-design, and be nevertheless consistent with small blow down, the efficiency of the valve as a relief device will be increased. By the employment of my invention the regulative parts of the valve are of such propor'tions'and are so located that small variations in machine work are of little or. no consequence,

and therefore it is easier to maintain practical uniformity in manufacture. In my improved safety valve herein described, the lift-regulating parts are centrally located, and are therefore of relatively small diameter, so that an error or variation in machining produces relatively little volumetric variation.

In the prevailing type of safety valve, it has also been observed that these valves have a considerably lower sustained lift at popping pressure than the lift to which they rise momentarily at the pop, and the difference between these two lifts is more than the increase in lift gained by the standard permissible 3% accumulation. Any lifting means employed to helpsuch valve during its accumulation period will necessarily become active at the pop so that the valve immediately pops into its high lift; or, in the alternative, if the lifting means does not become active at the moment of pop,

Specification of Letters Patent.

SAFETY-VALVE.

Patented Oct. 26, 1920.

Application filed October as, 1919. SerialNo. 332,750.

three per cent. accumulation will not be.

sufficient to bring it into action.

The class of safety valve to which this invention peculiarly relates is typified by the two-seated valve, in which the valve disk coacts with two concentric seats, and the apertures of egress from one of said seats (usually the inner and smaller one) afford means of control of thelift of the valve disk. Heretofore such safety valves have afforded. a fixed though adjustable- 0011- trolling cross section in said apertures, and the effectiveness of control diminished rel atively as the valve disk rose and increased the effective cross-sectional area of the main avenue of egress which included the opening between the disk and the outer and larger valve-seat.

Broadly speaking, my invention herein described is characterized by means for progressively constricting the effective crosssectional area of the control apertures of egress as the valve disk rises to predetermined lifts, so that the effectiveness of con trol by said control apertures keeps pace with the changing condition of lift, and is a powerful factor when control-poweris .needed the most.

The safety valve herein described will give of its pop lift; its action, instead of being abrupt, is more deliberate than the explosive action of modern high pressure valves of the prevailing type. y

In the drawings hereto annexed which illustrate my invention,-

Figure 1 is a vertical cross section of a safety valve which embodies my, improvements; and I V Figs. 2 and 3 are fragmentary views showing different forms of adjustable regulating device. I is the base of the valve adapted to be secured to a boiler and provided with two concentric valve seats at E and F. The disk valve B makes a sliding fit in the lower lip of the valve hood, and has, preferably formed integrally with it, a tubular skirt J which makes a sliding fit in the base and is located just inside the inner valve seat F.

The disk valve itself is centrally perforated at L,this perforation constituting a vent from the tubular interior of the skirt J through the valve head, which contains the usual loading spring G, to the atmosphere by way of suitable apertures H. The skirt J is laterally apertured at points close to the junction between the skirt and the disk of the valve, these apertures being shown at K. Preferably, also, an annular huddling chamber is formed at N inside the inner valve The action of a safety valve comprising elements such as are exemplified in the structure shown in the drawings is as follows: Aside from the action of the huddling chamber N which may, and preferably will be provided, when the pressure in the boiler rises to the point at which the valve is set,

the disk valve B will lift slightly, and as the apertures K present themselves for egress of steam, producing pressure in the tubular interior of the skirt J and thus giving the disk B an added lifting impulse which is responded to until compression of the spring G producesequilibrium.

Preferably, for purposes of control and, regulation, the constricting device exemplified by the tapered spindle O operates pro gressively as the disk B lifts to constrict the available free vent at. L, thus enhancing the aggregate disk-lifting pressure. At the same time, as more and more of the area of apertures K is exposed, more steam will be admitted into the interior of the tubular skirt J, emphasizing the tendency to further lift of the disk, which of course always retains itself in practical equilibrium with the spring Gr. When conditions which "cause excess pressure in the boiler have passed, the disk moves downward with decreased pressure, thus increasing the vent at L and decreasing the steam egress apertures K; continued decrease in lift will finally cut down the pressure in the skirt J to such value that the valve will close quickly after blowing down. For the sake of securing a quick and sensitive pop, it is advisable to employ the huddling chamber N in conjunction with the above described controlling and regulating factors; for when the boiler pressure starts the disk B off of its seats the presence of the huddling chamber instantly brings into play additional lifting area, and insures a quick pop; and also when, upon subsidence of boiler pressure and descent of the valve disk, the auxiliary sustaining and lifting pressure inside the tubular skirt J is cut down to such a value that the valve disk closes, its final closure, which might otherwise be too abrupt, is cushioned by the momentary accumulation of pressure in the huddling chamber N which is caused by the final constriction of p the apertures K.

"The adjustable spindle 0 permits variations in the initial area of the vent L. The smaller this area, the more quickly will the pressure inside the skirt J be built up, and hence a higher lift will be produced, With a consequent increase in blow down; Since the pressure in the interior of the skirt J is affected by variation in size of the vent L, this pressure and hence the lift may be changed by varying the shape of the effective end of. the adjusting spindle. Thus in Figs. 2 and 3, possible variations in the working end of the spindle are shown. The conoidal form of Fig. 2 will give higher lifts with the same blow-down than. will be the case when the spindle has a conical end, as in Fig. 1. If the form shown in Fig. 3 be employed, comparatively low pop lift will be secured, but there will be a second sudden lift when accumulation of pressure has raised the disk to a point where the upper conical step on the spindle becomes effective to constrict the vent area.

Furthermore, any of the above suggested methods of affecting the action of the valve may be further modified by varying the shape of the apertures K which admit steam into the central. well formed by the interior of the skirt J.

If the adjusting spindle 0 were to be eliminated and the orifice L increased in size so that there could be no appreciable pressure sustained in the tubular interior of the skirt and disk, all the parts necessary to provide a safety valve operating in the ordinary manner will remain if the huddling chamber N and vent K are present. The annular chamber N will then be the huddling chamber, and the area on the disk between the tubular skirt and the circumference of the inner seat F is the exposed area which causes pop and lift; the apertures K perform the function which the external blow-down ring in the usual type of valve performs. Such a valve will function completely as a safety valve and give lift diagrams which do not vary substan tially from those secured from valves of the prevalent commercial type. The lift may be increased by increasing the diameter of the inner seat F, this, however, not without increasing blow-down. Lifts obtainable under such conditions as are now being described are necessarily low because'of the small area which will be exposed when the valve is designed to give blow-downs of reasonably small value.

Moreover, in valves wherein a controlling spindle such as O is used, the spindle may be adjusted to such a positionthat it will take effect in conjunction with the vent L only under accumulation conditions. This implies a design such that pressure in the well will only exist in substantial value after accumulation has taken place, and imnominal seat area which lies outside the line of the seat contact at the outer seat; the steam employed to produce lift and regulation is only a small percentage of the total steam discharged, and is not quantitatively proportional to the lift and may be varied in quantity between wide limits according to requirements; the spring load area of the disk is smaller per inch of nominal valve diameter than is the case in existing valves; and the volume of the inner tubular portion or well is very large in comparison with the huddling chamber of the conventional type of valve, so large that the valve does vnot rise on the pop to a greater lift than it will sustain after the pop at the same pressure. This last mentioned feature makes a very hi h accumulation factor possible.

Vhat I claim and desire to secure by Letters Patent is: g

1. In a safety valve, a centrally perforated valve disk, concentric seats for said valve disk, of which the inner is adjacent to the central perforation in the disk, and means to constrict the effective area of egress from said inner seat as the valve disk rises.

2. In a safety valve, a base provided with concentric seats, a valve disk seating thereon, and means controlled by movement of the valve disk to constrict the effective area of egress from the inner seat as the valve disk rises.

3. In a safety-valve, a base provided with two concentric valve-seats, a disk-valve seating thereon, said disk-valve centrally perforated and provided with a tubular skirt in sliding engagement with the base inside the inner valve seat, said skirt being laterally apertured to admit pressure to its tubular interior when the disk valve is raised from its seats, and means to construct the vent provided by the central perforation in the disk-valve, as the valve rises.

l. In a safety-valve, a base provided with two concentric valve-seats, a disk-valve seating thereon, said disk valve centrally perforated and provided with a tubular skirt in sliding engagement with the base inside the inner valve seat, a huddling chamber between the inner valve seat and the tubular skirt, said skirt being laterally apertured to admit pressure to its tubular interior when the disk valve is raised from its seats.

5. In a safetywalve, a base provided with two concentric valve-seats, a disk-valve seating thereon, said disk valve centrally perforated and provided with a tubular skirt in sliding engagement with the base inside the inner valve seat, a huddling chamber between the imier valve seat and the tubular skirt, said skirt being laterally apertured to admit pressure to its tubular interior when the disk valve is raised from its seats, and means to constrict the vent provided by the central perforation in the disk valve, as the valve rises.

6. In a safety-valve, a base provided with two concentric valve-seats, a disk-valve seating thereon, said disk-valve centrally perforated and provided with a tubular skirt in sliding engagement with the base inside the inner valve seat, said skirt being laterally apertured to admit pressure to its tubular interior when the disk valve is raised from its seats, and a tapered spindle at the central perforation in the disk-valve, to constrict the vent provided thereby, as the valve rises.

7. In a safety-valve, a base provided with two concentric valve-seats, a disk-valve'seating thereon, said disk-valve centrally perforated and provided with a tubular skirt in sliding engagement with the base inside the inner valve seat, a huddling chamber between the inner valve seat and the tubular skirt, said skirt being laterally apertured to admit pressure to its tubular interior when the disk valve is raised from its seats, and a tapered spindle at the central perforation in the disk valve, to constrict the vent provided thereby, as the valve rises.

8. In a safety-valve, a base provided with two concentric valve-seats, a disk-valve seating thereon, said disk-valve centrally perforated and provided with a tubular skirt in sliding engagement with the base inside the 

